1. Technical Field of the Invention
This invention relates to archery and bow hunting equipment. More particularly, and not by way of limitation, the present invention is directed to a system and method for sighting-in an-archery sight for various target distances and determining the velocity of an arrow shot from the bow.
2. Description of Related Art
It has long been known to provide archery bows with sights to improve the accuracy of arrows shot from the bow. Such sights are typically mounted on the riser of the bow, above the handle and resting location of the arrow. While various sight arrangements are known, it is common to provide a plurality of pins which extend laterally from the riser to a position above the arrow. The pins are vertically spaced with each pin acting as a sighting indicator for a particular target distance.
When an arrow is shot from the bow, its flight is substantially ballistic. Therefore, the angle of launch will determine the distance that the arrow travels. In use, the archer gauges the distance to the target and visually aligns the head of the appropriate pin on the desired impact point for the arrow. As such, the uppermost pin (corresponding to a low launch angle) is typically set to correspond to a 20-yard flight. The lowest pin (corresponding to a high launch angle) is set for a greater distance such as 60 yards, and the intermediate pins may be set for intervals such as every 10 yards therebetween.
Each of the pins must be individually set in the proper position for each of the desired distances. This is typically done in a time-consuming calibration process in which the archer shoots arrows at targets that have been laid out at the various distances, and through a trial and error approach, each pin is painstakingly adjusted to match the point of impact for the arrow at the pin""s corresponding distance. This process is then repeated for each pin until all of the pins have been adjusted. As can be readily recognized, this is an extremely time-consuming process.
One proposed solution to the above-identified problem, is shown in Dixon et al. (U.S. Pat. No. 5,239,760). Dixon discloses an archery sight in which the pins are laterally mounted in a movable pin carriage and extend through slots in a fixed slide plate. The slots are linear and have increasing, yet proportionally constant spacing therebetween such that fore and aft movement of the pin carriage with respect to the slide plate causes the pins to move along the various slots and to expand or contract the distance between each pin. The archer then adjusts a first pin for a first desired distance using the existing trial and error method. The archer then places a target at a second distance and repeats the trial and error process for a second pin which is adjusted by moving the pin carriage forward or rearward along the slide plate. Dixon proposes that all of the other pins will then be in the proper position for the remaining predetermined distances due to the fixed proportional spacing provided by the slots in the slide plate.
The Dixon sight, and the process disclosed in Dixon for setting the pins, have several disadvantages. First, the archer must still use the time-consuming trial and error method to set two different pins for two different target distances. This creates a problem for the archer, not only because of the time involved in the process itself, but because it requires the archer to find a location suitable for shooting arrows at distances greater than 20 yards (the typical setting for the uppermost pin). This is a problem because indoor archery ranges are set up for shooting at 20 yards. For a longer distance, the archer has to find an open field, usually outside the city limits where he lives, where he can measure out the longer distance, set up a target, and shoot at the target so that he can properly align the second sight pin for the longer distance. Another problem with the Dixon sight is that it is not accurate enough for competition archery. The linear slots utilized with the slide plate are only an approximation of the sinusoidal function that defines the true ballistic flight of the arrow. Dixon admits that the linear slots are a compromise, but for competition archers, such a compromise is not acceptable.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a system and method for sighting-in an archery sight for various target distances that requires that only one pin be set with the trial and error method for 20 yards. In addition, such a system and method may be utilized to determine the velocity of an arrow shot from the bow. The present invention provides such a system and method.
In one aspect, the present invention is directed to a system for adjusting sighting pins for a plurality of target distances in an archery sight having a plurality of laterally-mounted, vertically-spaced sighting pins. A first sighting pin has been adjusted for a first target distance. The system includes an archery target with a horizontal reference indicator, and means for determining a vertical offset distance from the horizontal reference indicator. The offset distance indicates where an arrow destined for the horizontal reference indicator on an imaginary target at a second target distance would strike the target when mounted at the first target distance. The system also includes means for marking on the target, a vertical offset impact point at the vertical offset distance from the horizontal reference indicator. Finally, the system includes means for adjusting a second sighting pin corresponding to the second target distance to visually overlie the horizontal reference indicator when the first sighting pin is aimed at the vertical offset impact point. By determining vertical offset distances corresponding to a plurality of target distances, a plurality of sighting pins can be adjusted in a similar manner.
In another aspect, the present invention is directed to a method of adjusting sighting pins for a plurality of target distances in an archery sight mounted on a bow and including a plurality of laterally-mounted, vertically-spaced sighting pins. The method includes the steps of mounting an archery target with a horizontal reference indicator at a first target distance, and adjusting a first sighting pin for the first target distance, by iteratively shooting a series of arrows at the target and adjusting the first sighting pin until the first sighting pin visually overlies the point of impact of an arrow. When the velocity of an arrow shot from the bow is determined, the method determines a vertical offset distance from the horizontal reference indicator. The offset distance indicates where an arrow destined for the horizontal reference indicator on an imaginary target at a second target distance would strike the target when mounted at the first target distance. This is followed by marking on the target, a vertical offset impact point at the vertical offset distance from the horizontal reference indicator; and adjusting a second sighting pin corresponding to the second target distance to visually overlie the horizontal reference indicator when the first sighting pin is aimed at the vertical offset impact point. By determining vertical offset distances corresponding to a plurality of target distances, a plurality of sighting pins can be adjusted in a similar manner.
In yet another aspect, the present invention is directed to a method of determining a velocity of an arrow shot from a bow having an archery sight mounted thereon. The sight includes a plurality of laterally-mounted, vertically-spaced sighting pins corresponding to a plurality of target-distances. The method includes the steps of adjusting a first sighting pin for a first target distance by iteratively shooting a series of arrows at a target mounted at the first target distance and adjusting the first sighting pin until the first sighting pin visually overlies the point of impact of an arrow. This process is then repeated for a second pin and a second target distance. This is followed by shooting an arrow at a target mounted at the first target distance while aiming at a reference indicator on the target with the second sighting pin. A vertical offset distance on the target is then measured between the reference indicator and the point of impact of the arrow. This is followed by calculating the velocity of the arrow using the formula V={square root over ([Kxc3x97D2xc3x97(D2xe2x88x92D1)÷Y])}, where V is the velocity of the arrow (in feet-per-second), K is a multiplication factor defined for each target range, D1 is the first target distance (in yards), D2 is the second target distance (in yards), and Y is the measured vertical offset distance on the target.